Biodegradable copolymer compositions as well as their use as carriers for biologically active materials have been described in the prior art, both in the general literature and in the patent literature. In fact, many biodegradable copolymers have been developed for medical applications, and more particularly for the encapsulation of drugs.
In the patent literature, some disclosures in the area of biodegradable copolymer compositions are directed to the use of diblock, triblock or multiblock copolymers which consist of sequenced structures, wherein segments of various natures (e.g. hydrophobic and hydrophilic segments) are covalently linked together. WO 02/39979, U.S. Pat. No. 5,221,534 or U.S. Pat. No. 5,756,082 provide examples of preparation of such structures and describe their uses as drug delivery systems, as well as in cosmetic compositions or other applications.
On the other hand, by opposition to sequenced structures, grafted structures based on biodegradable polymer compositions have also been the object of patents and patent applications. In particular, systems based on the grafting of single polymers along polysaccharide chains have been disclosed. WO 01/79315 describes for instance copolymer compositions consisting of a hydrophobic macromolecule such as a polylactic acid cross-linked with a water-soluble polymer having multiple hydroxyl functionalities which may serve as potential reaction sites. The described composition can be used as a controlled drug delivery system.
More recently, US patent application 2002/0146826 has described a system based on a polysaccharide chain which has been grafted with an oligoamine on the one hand, and by at least one further group selected from the group consisting of a hydrophobic and an amphiphilic group. The oligoamines are conjugated with at least one oligomer per five saccharide units, whereas the hydrophobic and amphiphilic groups are positioned with at least one group per 50 saccharide units. The document discloses the application of the systems to gene therapy.